Locating a septic tank, distribution box, and field lines can be a frustrating and expensive experience for a homeowner and even for a professional septic service company. The University of Minnesota Extension service publication PC-06583, incorporated by reference herein, recommends tracing the sewer pipe exit from the house, and then with a rod or probe poking around in the soil 10 to 15 feet from the foundation of the house. The University also suggests that a metal detector may be of assistance since concrete septic tanks may contain metal reinforcing rods. However, modern fiberglass tanks will not contain any metal. The University suggests looking for greener grass, depressions, mounds, or wet spots to find the field lines.
These techniques are ratified as state-of-the-art by eHOW in How to Find a Septic Tank; The Laundry Alternative Inc. in How to Locate a Septic Tank; and A-1 Cesspool Service Inc. in Locating your Septic Tank: all three of which are incorporated by reference herein. A homeowner will typically use a hammer and piece of pipe or rebar as a probe. A commercial septic service will usually have a tool with a handle, such as the Subsurface Tool of Thompson in U.S. Pat. No. 5,487,432, incorporated by reference herein. Some incorporate a driver similar to a metal fence post driver with a built-in sliding hammer.
Once the septic tank is located, the distribution box location may be narrowed down by proximity to the septic tank or running a fish tape through the discharge pipe and listening for the tape hitting the box. Locating the plastic or clay pipe field lines is more of a problem.
In U.S. Pat. No. 5,281,024, incorporated by reference herein, Fons discloses a Method for Locating Porus and Permeable Soils Employing Earth Surface Temperatures.
In U.S. Pat. No. 4,309,576, incorporated by reference herein, Corrigan discloses a Listening Device for Locating Underground Water Leakages, wherein an acoustic pick-up coupled to an amplifier-receiver, level meter, and headphone is used to probe the earth for the maximum signal strength.
In U.S. Pat. No. 4,911,012, incorporated by reference herein, Ziska discloses a Sewer Line Detection System wherein sound is injected into the pipe, and a listening device and sound meter is coupled to the earth to locate the line.
In U.S. Pat. No. 6,003,376, incorporated by reference herein, Burns et al. discloses an Acoustic System for Measuring the Location and Depth of Underground Pipe wherein sound is injected into a pipe and an array of transducers coupled to a computer locates the pipe.
In U.S. Pat. No. 6,679,120, incorporated by reference herein, Cribbs et al. discloses a System and Method for Guided Boring Obstacle Detection, wherein a drill head generates sound detected by an array of detectors to detect the presence or absence of an underground obstacle, such as a pipe.
In U.S. Pat. No. 7,336,078, incorporated by reference herein, Merewether et al. discloses Multi-Sensor Mapping Omnidirectional Sonde and Line Locators wherein a sonde can be attached to a push cable or line, or self-contained in a flushed transmitter such as U.S. Pat. No. 7,221,136, incorporated by reference herein, disclosed by Olsson et al.
The aforementioned methods are either trial-and-error, costly, or technically sophisticated. Moreover, there is no known use of the combination of synchronous detection with exploitation of acoustic resonance of a cavity to enhance the signal to noise ratio.
There is a need for a simple and economical instrument for locating underground utilities, such as, but not limited to, a septic system. Such an instrument is disclosed herein which is within the operational capability, and cost limitations, of a homeowner, septic service, or rental service.